The analysis of calcium current inactivation in rat intermediate lobe cells described in the previous report was completed. This study showed that the amplitude of the calcium current in these cells is strongly dependent on the prior history of the membrane potential. Thus, secretion from these cells may be regulated by small changes in the resting membrane potential. This project will be continued in the cultured chick ciliary ganglion neuron model. We will test how many types of calcium channel occur in these cells and whether these channels are located in the cell body, the axon or the nerve terminal. The role of resting membrane potential in modulating calcium currents in neuronal cells will also be tested.